Control of relays



June 23, 1925. u 1,543,125

H. R. ROBINSON CONTROL OF RELAYS Filed April 2l. 1924 CZ l Z 3 P/are am f Patented June 23, 1925.

UNITED vSTATES PATENT OFFICE.

HUGH R. ROBINSON, or BROOKLYN, NEW YORK, AssrGNoR To WESTERN ELECTRIC COMPANY, INCORPoRa'rRn, or NEW YORK, N. Y., n CORPORATION or YORK.

CONTROL F RELAYS.

Application led April 21, 1924. Serial No. 707,862.

To all whom z't 'may omwcm:

Be it known that I,A Hoor-rv R. ROBINSON, a citizen of the United. States of America, residing at Brooklyn, in the county of Kings and State of NewYork, have invented certain new and useful Improvements in Control of Relays, of which the following isa full. clear, concise, and exact description.

This invention relates to relaying electrical variations, and aims to improve control of the relaying operation.

A particular object is to stabilize the electrical output characteristics of relay apparatus. f

For brevity and clearness, the invention is described hereinafter with special reference to its application to electric discharge relay apparatus involving a well-known form of three-electrode tube,- although not necessarily limited to apparatus of that type.

Another object of the invention is to reduce the tendency of variations of cathode energizing current to4 result in undesired electrical variations in the output circuit of the relay. f

Another Obfect of the invention is to reduce the tendency which changes in cathode heating current have to vary the voltage bias of the control electrode, or to vary this voltage bias and the voltage applied across the anode and cathode. It is desired to reduce this tendency especially where a plu,- rality of tubes have their cathodes in serial relation. i

.Ik still further object is to utilize a tube which is subject to filament voltage variations to'counteract the tendency that different filament voltage variations of another tube have to cause undesired electrical variations in a circuit connected thereto, It is Vespecially desired to employ thisy feature of the invention in order to maintain balance and reduce undesired gain variations 1n a push-pull amplifier having its cathodes conynected in series; and also to employ this feature in order to reduce carrier leak in a balanced modulation circuit having its cathodes connected in series.

In the forms of the invention specifically illustrated and described herein` the desired compensation' for variations of voltage of the cathode of a tube is obtained by shunting across the source of. voltage employed for heating the cathode, a circuit comprising a resistance and a source of potential for biasing the control electrode of the tube,

and connecting the control electrode to the proper point on this resistance, as pointed outy hereinafter. Where a plurality of tubes having their cathodes in series, ,referably a. separate resistance, such as that ]ust referred to, is employed for each of the tubes, and a common source of grid potential maybe employed, with the resistances all connected to proper points on thebattery, as pointed out hereinafter. In a balanced tube circuit, as for instance in a push-pull amplifier or a balanced modulator, by properly compensating each tube for variations of its voltage, the balance of the circuit is maintained, and undesired gain variations of the circuit are reduced, and, in the case of the modulator, by amaintenance of'balance the carrier leak is reduced.

Further objects and advantages of the invention will appear from the following description of the drawings, of which Fig. l is a diagram for use in explaining certain fea-tures of the invention; Fig. 2 is a diagram of a form of the invention embodied in a modulating system for high frequency carrier Wave signaling in which the carrier current used for transmission is suppressed except when modulated at low frequency, the modulating device employed bemg of the thermionic type.

In many of the vacuum tube circuits used at present, any change in the filament voltage, and current produces changes in grid.

bias and applied plate potential which are of such relative values that the plate current changes. For instance, when the biasing battery (or other source of grid potential) and the plate battery (or other source of plate current) are connected to the positive side of the filament, an increase in filament voltage causes a decrease in the'plate .resistance and an increase in the space current due to two changes: the decrease in the value of applied negative grid potential and the increase in applied plate potential. (The change in electron emission is here neglected since the tubes usually operated in the saturation condition and the effect of change in emission is consequently of little importance.) Furthermore, when filaments of two or more tubes are connected in series and the tubes are supplied from the same sources of grid and plate potential, vthe effect is greater than when the tubesarther from the common point are supplied from the sources of filament current, plate current,

and grid potential. This is especially dis- -advantageous in circuits of the balanced type, such as balanced modulators or, demodulators, and push-pull or other balanced amplifiers.

A circuit will now be described which embodies means for either maintaining the grid bias constant or varying it to compensate the changes in plate resistance and applied plate voltage due to variation of filament voltage, regardless of the position of the tube in the circuit.

Referring to Fig. 1, three electron'discharge tubes 1, 2. and 3, which may be of the well-known three electrode type comprising anodes, ilamentary cathodes, and grids, have their filaments connected in series. These tubes are intended to represent a plurality of tubes connected in any desired input and output circuits. 'Therefore, and in order to avoid complication in the drawing, the input and outputcircuits were not shown in Fig. 1. One possible arrangement of input and output circuits for a plurality of such tubes, used inaccordance with the invention, will be set forth later in connection with the description of Fig. 2. In Fig. 1, preferably a common plate battery 5 supplies plate current for each ot' the tubes 1, 2, and 3. A common l'ilament battery 10, having its positive pole connected to the negative pole of the plate battery 5, supplies heating current for the cathodes of tubes 1, 2, and 3, this current liowing from battery 10 through the filament of .tube 1, the filament of tube 2, the filament of tube 3 and preferably through a resistance 11 and an adjustable resistance 12, back to the filament battery. The resistance 12 may be used to adjust the filament current, and the resistance 11 may be used to adjust the voltage across battery 10 and resistance 12.

Preferably, a common grid battery 20, having its positive pole connected to the positive pole of the filament battery 10, supplies potentials for the grids of tubes 1, 2,

and 3. The grid of tube 1 is connected toV the junction point of two resistances, b, and d1, which are connected in series with each other between a point onv the grid battery 2|) and the junction of the resistances 11 and 12. Similarly, the grid of tube 2 is connected tothe junction of two resistances, );i and d3, which are connected between another point on the grid battery 20 and the junction of resistances 11 and 12. The dotted portions of the 'leadsl between the grids of the tubes and the resistances b1, all, the resistances b2, (Z2, and the resistances bm da, res ectively, are intended to indicate any desire sources of input voltage for the tubes. The resistances b1 and d1, the resistances b, and d2, and the resistances b, and da, are preferably large enough to make no great current drain on the grid battery 20. It will now be explained how the desired compensationfor changes of filament current can beA made for each tube so that' upon variation o the filament current, the resultant change in grid potential will substantially neutralize the eli'ect, upon the plate current, of the resultant change `in the applied voltage across the anode and cathode; or, if desired, so that the grid poten` tial remains constant upon variation of the filament current.

Let G designate the negat've potential desired on the grid of any given one ofthe tubes. (Thus G, on the drawing'indicates the potential difference between the grid land the midpoint of the filament of tube' 2,

the subscript of G indicating the particular tube involved. Where no subscript is employed, the designations apply to the re- 8. sistances, voltages, etc. for any given one of the tubes.)

Let C designate the negative potential which is necessary to obtain from the grid battery 20, the grid of the given tube. (For instance, C2, in Fig. 1, designates the crresponding potential difference across the part of the grid battery 20 employed to supply biasing potential for the grid of tube 2.)

Let A- designate the voltage drop across battery 10 andl resistance 12, as indicated in Fig. 1. Let the voltage drop in the lament of the iven tube be designated by F, as indicated by the drops at F1, F2, and F3 in Fig. 1. 10u

Let K designate the ratio of the voltage drop between the electrical midpoint o the ilamentand ground. y (Positive pole of Vtilament battery to the total voltage drop (A) in the filament circuit. Thus K, X A, in Fig. 1, designates the voltage between the positive end of battery 10 andthe electrical midpoint of the Element of tube 2.)v

Let M designate the voltage'amplification constant of the tube. v

The formulae for obtaining the desired compensation, to maintain constant plate current under variations of filament current, will now be stated, and the derivation will be given. These formulae are based onA the supposition that the grids 'never becomeA positive with respect to the filament, and K is a constant, and that no allowance is to be made for changes of electron emissionrom the filament. The formula: are:

` K b n K+M d 1 ir-K d Vd (Vd -l-Vb) For every chan e in A,AA, there is a change in G,A G. he change in plate p0- tential is K A A and thev compensating lVhen itI is desired to maintain a constant grid bias, M may be considered infinite, (the condition to make an infinitely small change inv grid potential compensates for any finite change in applied plate potential), and the formulae'become:

dnl-K and G @mit 2 illustrates an application of the invention to a modulator of the general type disclosed in Fig. 4 of J. R. Carson Patent 1,343,306, June 15, 1920. In Fig. 2, tubes 1, 2, and 3 corres 0nd to the tubes 1, 2, and 3 respectively o Fig. 1. Similarly, plate battery 5, filament battery 10 and grid battery 20, of Fi 2 correspond to the batterles 1, 10, an 20 of Fig. 1. Also, resistances 11 and 12 of Fig. 2 correspond to the similarly designated resistances of Fig. 1; and resistances d1, b1, b2, correspond to the similarly designated resistances of Fig. 1. For simplicity, Fig. 2 shows no resistances corresponding to resistances 25'3 and d, of Fig. I, since Fig. 2 is not necessarily intended as indicating 2, 3 as compensating for changes in filament heating current. Tubes 1 and 2, in Fig. 2, are preferably similar'and equal in their structure and characteristics. The-input circuit of tube 1 includes a secondary winding 411 of a transformer 41, the primary winding 412 of which is included in series with the source variations O. The input lcircuit of tube 2 includes the secondary winding 413 of the transformer 41. In series with the Winding 411 is included a secondary Winding of a transformer 44 and in series with the' winding 413 is included a secondary winding of a transformer 442. The transformer 411 has a primary Winding inseries with a primary winding of the transformer 442, in an incoming circuit 42 leading to a source of low frequency signal current such, for example, as a telephone transmitter (not shown). Direct current biasing' otential is supplied b battery 2O to the grid of the tube [from t 1e junctlon of resistances d, and b, through winding 411l and the secondary winding of transformer 44,. Similarly, biasing potential for the grid of tube 2 is supplied by battery 20 to the grid of tube 2 from the junction of resistances d2 and b., through the winding 413 and the secondary windi'n of transformer 442. A condenser 60 furnlslies a low impedance path for current variations from source 0 between the winding 411y and the filament' of tube 1. Similarly, a condenser 6l furnishes a low impedance path for the current variations from source O between Winding 413 and the filament of tube 2. The condensers and 61 in series furnish. a low impedance path for the low frequency signaling currents from circuit 42 between windings 411 and 413.

The output circuits of tubes 1 and 2 are connected in parallel with respect to the battery 5 which is arranged in a common conductor of said circuits. The output circuit of tube 1 includes a primary winding 46 of a transformer' 481, and the output circuit of tube 2 contains a primary winding 47 of a transformer 482. The. secondary windings of transformers 48L and 48, are connected, in series, to anoutgoing circuit 50. Lead shown in dotted lines is to indicate that the battery 5 may supply plate current to other circuits, for instance, like that of Fig. 2. Similarly, leads 71 and 72 are to indicate that the battery l() may supply filament heat-ing current to lother circuits such for instance, as that of Fig. 2. Also, the lead 74, and the leads 73 and 7 3', are to indicate that the battery 2O may supply voltage to other grid biasing circuits, for example, like those of Fig. 2. l

Normally, when no currents are impressed upon circuit 42, the high frequency oscillations from source O acting through transformer 41 impress equal voltage variations of the same phase upon the grids lof tubes 1 and 2, thereby producing equal iiuctuations of the samev phase in the output circuits. `The windings of transformers 48l and 482 are so arranged that circuit 50 is differentially coupled to the two output circuits, the fluctuations in the output circuits neutralizing each other with regard to their effects upon the outgoing circuit 50. -When low frequency current variations from circuit 42 are impressed upon the repeater circuit lthrough transformers 441 and 442, the high frequency potential variations are augmented upon one grid and decreased upon the other, producing correspondingly augmented fluctuations inthe one output circuit and correspondingly reduced fluctuations in the other. The fluctuations in the output circuits are no longer balanced, and consequently oscillations are produced in the output circuit -50 which have an amplitude proportionate to the instantaneous value of the low frequency modulating currents coming from circuit 42. It is therefore seen that carrier waves are suppressed except when signaling currents are applied.

As pointed out in Blattner Patent 1,483,-

273, February 12, 1924, in a push-pull ampliiier, the tubes of whichliave their filaments heated from a common source of voltage, each of the tubes tends to prevent yoltage variations of the output current of the other tube, due to variations of the voltage of the heating source, from causing' current variations in the outgoing circuit connected to the amplifier, for, as noted in the Blattner patent, at any instant when the heating currents would tend to increase the average difference of potential between the cathode and the grid or the anode of one of the tubes, the heating current would tend to increase the average difference of potential between 'the cathode and the grid or the anode of the other tube. action occurs whether or noty the grid and plate of each tube is connected to an intermediate point on an. impedance across the filament as in Heising Fatent 1,432,022, October 17, 1922. However, as pointed out above, where the filaments of the push-pull amplifier tubes are in series and the tubes are supplied from common sources of grid and plate potentials, the eect of voltage variations in the cathode beating source is greater upon the plate or grid potentials of one of the tubes than upon the plate or grid potentials of the other tube, and consequently it is likely to'unbalance the tubes and cause undesired current variations in the outgoin circuit connected to the pushpull ampli er, unless some preventitive means is employed. By compensating the tubes 1 and 2 of Fig. 2 for changes of {ilament battery voltage, as the tubes 1 and 2 of Fig. 1 are compensated, each of the tubes 1 and 2 of Fig. 2 has its output current main'- tained constant, its rrid potential variations due to changes of its cathode voltage just counter-acting the eii'ect of its plate potential variations due to the same cause; or if desired, the grid potentials of each of the tubesmay be maintained constant in the manner explained above in connection with -the description of the operation of tubes 1 and 2 in Fig. 1.

In the circuit of Fig. 2, constant direct current vvin the output circuit of each of the tubes 1 and 2 results in preventing carrier current from appearing i'n the outgoing circuit 50 connected to the tubes (or, in other words, prevents carrier leak), and also maintains constant gain of the push-pull amplilier under 'changing filament battery voltage, and further reduces noise currents, which variations of filament battey voltage tend to create'.

The principles of the invention claimed ma be embodied in many organizations di ering widely from those specitigally illustrated and described.

1What -is claimed is:

1. An ener translating system comprising an electric discharge device having an anode, a cathode, and means for controlling current flow between said anode and cathode, voltage supply means for energizing said cathode, a generator of electromotive 'force This mutual compensatingforsuppiying voltage across -said anode and cathode, a generator ofelectroinotive force Said cathode energizingoneens,V andfmeans connecting. said control*y means to, a point of one of rsaid, paths at a ,potential different roxlithe. potentials'of'the ends of said one pat 2. Anenergy translating system comprisfing an electric discharge devicehavingan anode,a cathode, and a, control electrode for controlling current ilow between said anode and cathode, voltage supply" means for venergiaing said cathode, sa-id .means i having thereon two points of different potential, a

enerator of electroinotive yforce 4for su pl in g vvoltage' across said' anode and catho le, a generator 'of electromot-ive force for supplying biasing lpotential fto said control electrede, said bia'sin generator having thereon two'poin'ts of di erent'potential,l means connecting one'of Said points on said biasingv generator to one of said points onsaid cathodeenergizing means, a resistance .con-

necting said other point on said biasing-generator to said other pointon' said cathode energizing means, and 4a connection (from 'said control electrode to a point'on ysaid vresistance'between its ends.

'l An ener vtranslating system comprisingan electric dischargedevice having -an anode, a cathode5anda'control electrodeA forv Icontrollin current flow between said-'anode and catho ve, voltage supply means for ener? gizingsaid` cathode, said means having thereon vtwo points of differentpotential, a generator ,of electromotive force for supplying` voltage across. said-,anode and cathode, va generatorof electromotivegforce for supplying vbiasing potential to 'said control electrode, ksaid biasin eneratorlhavin thereon two points fof i l means comprising a resistance connecting the more negative of saidlast two pointsto one of said `first twofpoints`,. means connect ing the reinainingtiivov of. said. four points, and a connection from said control electrode to a point'on said resistance' between its ends.

' 4. An energy'translating an electric ,dis-

charge device having. an anode, a cathode, and a. control, electrodel for controlling lcurrent flow betweensaid-- anode and cathode Avoltage supplymeansfor energizing sai cathode, said meansv having thereon two points of different potential, a generator of electromotive force v.for sup lying voltage across said anode and ,catho e, a generator of electroinotive force for suppifing" biasing potential to said controlelectro e, said bias,-l inv generator having thereon two'points of div e'rent potential, means comprising a resistance connecting the more negative of erent `potentie connection from said control electrode to a point on said resistance between its ends. fAnvenergytranslating system comprising an electric 'discharge device having an anode, a cathode, and a controlelectrode for controlling current flow between Said anode and cathode, voltage supply means for energiz'ing said cathode, said means having thereon two points of ,different potential, 'a generator of electromotive force for suppl ing voltage across said anode and cathode, a generator of electromotive force forf'snp# plying biasing potential to said control elecf tro'de, said biasin lgenerator having thereon twopoints of diigerentpotential, means connecting one of said points on said biasing generator lto one vof rsaid points rvon said cathode energizing means, a resistance connectii'ig" said other pointf on said biasing generator to said'fother` oint on said cathode energizing means, an a connection from said control electrode tosuch -a point on said resist-ance las to compensate for the eiect of variations ofvoltage of said cathode energizing meansl upon the value offsaid current between said cathode and said anode.

6. An energy'translating systemcomprisfing an electric discharge device having --an plying biasing potential to said'icontrol electrode, said biasing generator 'having thereon two,r points of different potential, means comprising a resistanceco'nnecting the' more negative of'said last two points tothe more ino negative of-fsaid first two points, land a conneetion from said eontrol electrode to such a point .on said resistance as to compensate for the effect of variations 0f voltage of said cathode energizing means upon the potential of said control electrode.`

7. An energy translating system comprising an electron discharge tube having an anode, a cathode, and a controlelectrode for controllin current flow between saidl anode and catho e, voltage supply means for energizing said cathode,l said means having therQOn-a point 0f one potential` and a point of lower potential, a generator of electrometive :force .for lsii'pplying voltage across said anode and cathode, a generator of electro# motive force for supplying biasing potential to said control electrode, saidbiasing generator `-having thereon two i v l y pointsfof vdifferent potential, means comprising a resistance connecting the more negative of said last two points to the more negative of said iirst two points, means connecting together the remaining two of said four points and said generator for supplying voltage across said anode and cathode, and a connection from said control electrode to such a point between the ends of said resistance as to compensate Jfor the effect of variations of voltage of saidcathode energizing means upon the potential of said control electrode.

8. An energy translating system comprising an electron tube having an anode, a cathode and a control electrode for controlling current iow between said anode and cathode, a voltage supply source, a circuit connected across said source and including said cathode, a circuit shunted across said first circuit and including an electromotive force generator, and a connection from said control electrode to a point on said second circuit.

9. An energy translating system comprising a plurality of electron tubes each having an anode, a cathode, and a control electrode, means connecting said cathodes in series with each other, -means for energizing said series 'connected cathodes, said energizing means being thereon points of different potential, electromotive force generating means-for supplying biasing potentials to said control electrodes, said biasinfr venerating means havingv thereon points o? di'erent potentials'one'of which is connected to one of said points on said cathode energizing means, resistances respectively connecting said other points on said biasing generating means to said other points on said cathode energizing means, and connections from each of said controlelectrodes to a point between the ends of one of said resistances, respectively. I

10. An energy translating system comprising a plurality of electron tubes each having an anode, a cathode, and a control electrode, means connecting said cathodes in series with each other, means for energizing said series connected cathodes, said energizing meanshaving thereon points of different potential, electromotive force generating means for supplyingl voltagel across said anodes and cathodes, common electromotive force generating means for supplying biasing potentials to said control electrodes, said biasing generating means having thereon points of different potentials one of which is connected to hi liest potential one of said points on' said cathode energizing means and to said means for supplying voltage across said -anodes andcathodes, resistances respectively l connecting said other points on said cathode energizing means,'and' connections from each of said control electrodes to such a point between the ends of one of said resistances, re-

electric discharge apparatus connected be- I tween said circuits, said apparatus including a pair of cathodes and also including a pair of input circuits and a pair of output circuits, each of said input circuits and output circuits including one of said cathodes, the two circuits'of one of said pairs being oppositely associated with one of said first .two circuits, and at least one of the circuits of the other of said pairs being associated with the other of said first two circuits, means for energizing said cathodes in such manner that changes in the characteristics of said means tend-to eect the currents in said two output circuits in different degree, and means for counteracting said tendency.

12. In combination, two discharge devices, each having an anode and an electron emitting cathode for permitting space discharge current to How through said device, means supplying current of varying amplitude for rendering said cathodes active to emit electrons, means actuated in response to variations of said space discharge currents, the

variations of said current from said first means tending to produce two opposing but unequal eiiects upon said means, and means for substantially 'equalizing said last ei'ects.

13. A. translating apparatus comprising a pair of repeater circuit'sg'eftwo separate sources of current variations, said repeater circuits being symmetrically associated with one of said sources and being oppositely associated with the other source, an outgoing circuit associated with said repeater circuits, means for energizing each of said repeaters and subject to changes which tend to simultaneously produce two opposite but unequal effects-upon the control of one of said sources over said outgoing circuit, and means for equalizing said effects.

14.. A modulating system comprising a pair of translating devices, a source of high frequency energy similarly connected with said devices, a source of modulating energy oppositely connected with said devices, an outgoing circuit differentially connected wit said devices, means for energizing each of saiddevices and subject to change which Y tend to simultaneously produce two opposite but unequal effects upon thecontrol ofy said high frequency source over said outgoing circuit, and means for equalizing said effects.

15. A. modulating system comprising a pair of translating devices each including a. cathode, a source of high frequency energy similarly connected to said devices and including a cathode, a source of modulating energy oppositely connected with Said devices*` an outgoing circuit differentially connecteC- with said devices, means energizing all of said cathodes in series with each other and subject to changes which tend to simultaneously produce two opposite but unequal eects upon the control of vsaid high`frequency source over said outgoing circuit, 10 and means for equalizing said effects.

In witness whereof, I hereunto subscribe my name this 17th day of April, A. D. 1924.

HUGH R. ROBINSON. 

